adaptation
a heritable trait that enhances an individuals fitness
adaptive radiation
The emergence of numerous species from a common ancestor introduced into an environment, presenting a diversity of new opportunities and problems.
allele
alternative versions of a gene that produce distinguishable phenotypic effects.
allopatric speciation
A mode of speciation induced when an ancestral population becomes segregated by a geographic barrier or is itself divided into two or more geographically isolated subpopulations.
analogous structure
similar structures that evolved separately in different lineages
antibiotic resistance
the ability of a microorganism to resist the effects of an antibiotic to which they were once sensitive
artificial selection
the selective breeding of domesticated plants and animals to encourage the occurrence of desirable traits.
bottleneck effect
Genetic drift resulting from the reduction of a population, typically by a natural disaster, such that the surviving population is no longer genetically representative of the original population.
cladogram
diagram depicting patterns of shared characteristics among species
clades
a group of species that includes an ancestral species and all its descendants
common ancestor
an organism that is an ancestor of two different organisms that are not related to eachother
convergent evolution
process whereby organisms, not closely related,independently evolve similar traits as a resultof adapting to similar enviroments
directional selection
Natural selection that favors individuals at one end of the phenotypic range.
disruptive selection
Natural selection that favors individuals on both extremes of a phenotypic range over intermediate phenotypes.
divergent evolution
process by which interbreeding populations or species diverges into two or more descendent species, resulting in becoming mor dissimilar
emigration
movement of individuals out of a population
evolution
All the changes that have transformed life on Earth from its earliest beginnings to the diversity that characterizes it today
founder effect
Genetic drift that occurs when a few individuals become isolated from a larger population, with the result that the new population's gene pool is not reflective of the original population.
gene flow
Genetic additions to or substractions from a population resulting from the movement of fertile individuals or gametes.
gene pool
The total aggregate of genes in a population at any one time.
genetic drift
Unpredictable fluctuations in allele frequencies from one generation to the next because of a population's finite size.
homologous structures
structures in different species that are similar because of common ancestry
immigration
the influx of new individuals from other areas
isolation types
six different mechanisms that prevent the sperm and egg from coming together
limited resources
a resource which cannot be made available on a scale which can sustain its compstion rate
outgroup
A species or group of species that is closely related to the group of species being studied, but clearly not as closely related as any study-group members are to each other.
phenotype
the physical and physiological traits of an organism, which are determined by its genetic makeup
phylogenetic tree
A branching diagram that represents a hypothesis about evolutionary relationships.
population
A localized group of individuals that belong to the same biological species (that are capable of interbreeding and producing fertile offspring).
protobiont
An aggregate of abiotically produced molecules surrounded by a membrane or membrane-like structure
random mating
the choice of mates in which chance plays the biggest part
reproductive isolation
the existence of biological factors (barriers) that impede members of two species from producing viable, fertile hybrids
serial endosymbiosis
A model of the origin of eukaryotes consisting of a sequence of endosymbiotic events in which mitochondria, chloroplasts, and perhaps other cellular structures were derived from small prokaryotes that had been engulfed by larger cells.
speciation
origin of new species in evolution
species
A group whose members possess similar anatomical characteristics and have the ability to interbreed.
stabilizing selection
natural selection that favors intermediate variants by acting against extreme phenotypes
sterility
incapable of producing offspring
sympatric speciation
a mode of speciation occurring as a result of a radical change in the genome of a subpopulation, reproductively isolating the subpopulation from the parent population
variation
differences between members of the same species
vestigial organs
Structures of marginal, if any, importance to an organism. They are historical remnants of structures that had important functions in ancestors.
viability
capable of living